1. Field of Invention
This invention generally relates to interconnecting devices, such as integrated circuits, circuit boards, electrode arrays, or other devices.
2. Description of Related Art
As described in U.S. Pat. No. 5,613,861, standard bonding techniques for electrically connecting integrated circuits, or chips, to a circuit board or other device include wire bonding, tab bonding, solder-bump and gold-bump flip-chip bonding and other techniques. However, these standard bonding techniques suffer from various problems and limitations, including relatively low resistance to thermal and mechanical shock and being incapable of being made very small, e.g., allowing a contact pad pitch of several microns.
The invention provides a method and apparatus for interconnecting two devices by using an adhesive that surrounds the contact structures on the devices and adheres to the device substrates. According to the invention, the two devices are interconnected by first applying an adhesive to at least one of the devices. The adhesive can be applied so that the adhesive surrounds at least some of the contact structures on the device or can be applied away from the contact structures. As used herein, the term xe2x80x9ccontact structurexe2x80x9d can include contact pads, spring contact structures or other physical or electrical connection structures, and the term xe2x80x9cdevicexe2x80x9d can include any type of apparatus including circuit boards, semiconductor chips, a laser device, an optoelectronics module, etc. After the adhesive is applied, the devices and their corresponding contact structures are aligned and the devices are brought into sufficient proximity to allow the contact structures on the devices to interconnect, e.g., electrically interconnect. As the devices are brought into sufficient proximity, the adhesive can flow into areas where contact structures are present. Thus, even if the adhesive is applied to a device in an area where no contact structure is present, adhesive can flow around the contact structures during assembly. The adhesive is cured or otherwise hardened to bond the devices together.
The inventors have discovered that if an adhesive is applied, e.g., injected in a conventional fashion, between devices after the devices are electrically connected, the adhesive can disrupt the connection between the devices, especially if delicate spring contacts are used to interconnect the devices. Thus, the adhesive is applied to at least one of the devices before the devices are assembled.
In one aspect of the invention, the contact structure of at least one of the interconnected devices includes at least one spring contact.
In one aspect of the invention, a spring contact that is part of a device""s contact structure includes a stress gradient formed in the spring contact, which causes the spring contact to bend away from the substrate and thus provide compliant contact with a corresponding contact pad.
In one aspect of the invention, spring contacts included in a contact structure of a first device are formed of a thin metal strip which is in part fixed to a substrate and electrically connected to a via on the substrate. The free portion of the metal strip not fixed to the substrate bends up and away from the substrate. When a contact pad on a second device is brought into pressing contact with the free portion of the metal strip, the free portion deforms and provides compliant contact with the contact pad. Since the metal strip is electrically conductive or coated with a conductive material, the via on the substrate is electrically connected to the contact pad on the second device via the spring contact.
In one aspect of the invention, spring contacts can have various tip configurations, including a single point, multiple points, a deformable tab, a flat end, etc.
In one aspect of the invention, spring contacts can have various configurations such that portions other than a tip of spring contact are connected to a corresponding contact pad. For example, a spring contact can curl to form an arc of 180 degrees or more.
In one aspect of the invention, the contact structures of the devices can include various connection devices.
In one aspect of the invention, at least one of the interconnected devices can be or include an LED device, a laser emitting device or devices, a photodetector, microelectronics devices, an LCD device, a driver device, etc.
Other aspects of the invention will be apparent and/or obvious from the following description.